Machine for Bonding Films Made of Different Materials in Several Layers, and the Corresponding Method

ABSTRACT

This invention relates to a machine for bonding up to three film comprising:
         a first unit designed to unwind a first film associated with a spreader/applicator unit to apply an adhesive material to one surface of said film;   a second unit designed to unwind a second film associated with a spreader/applicator unit to apply an adhesive material to one surface of said film;   a third unit designed to unwind a third film; and   a fourth unit comprising two bonding machines designed to join the various layers of film together.       

     Said bonding units comprise a bonding calender, onto which the various layers of film are wound, and at least one presser roller which is subject to the action of hydraulic actuators, the two bonding units being positioned between the two pay-off/applicator units. 
     The present invention also relates to a method for bonding three films composed of materials which can be of a nature similar to and/or different from one another, using the same bonding unit.

This invention relates to a machine to bond a number of layers usingsolventless adhesive to obtain a single film consisting of a series oflayers (multilayer film), and the corresponding method. Moreparticularly, it is able to bond films composed of materials which canbe of a nature similar to and/or different from one another, and evenmore particularly, at least two films are composed of materials havingdifferent compositions such as plastics, paper or aluminium.

The machine according to the invention is configured to bond threelayers of film to one another; the operation can be performed in twodifferent ways. The first involves simultaneously bonding three layersof film, unwound from three different reels, in the same bonding device;in most cases, this is the solution that maximises the performance ofthe machine. The second procedure, which is necessary for some types ofmaterial, involves bonding the first two layers to one another in thefirst part of the machine, and subsequently bonding them to a thirdlayer in a second bonding device.

In the present description, the term “film” refers to the films that areunwound from the reels mounted on the machine; these films can be singlelayer or multi-layer films previously bonded.

Specifically, the machine comprises three pay-off units that feed thelayers of film, two of which are associated with spreader/applicatorunits. Each unit includes an adhesive tank and means for picking up saidadhesive and transferring it in a thin layer to an applicator rollerwhich moves in contact with the drum.

The various layers of film are conveyed to a bonding zone, where the twobonding devices and the finished product rereeler are installed.

The machine and the method according to the invention are highlyadvantageous, because they allow to bond two or more films in a singleoperation. Moreover, the finding of the present invention allows toprovide machines that are extremely compact in size being far smallerthan conventional systems which, in order to bond several layers,require the same number of bonding machines as the number of layers,connected in series.

Another advantage of the machine according to the invention relates tothe fact that it can also be configured for use as a machine for bondingtwo films only (Duplex action).

Bonding machines which bond two films while they advance, possibly athigh speed, using a solventless adhesive, are already available on themarket, such as the one described in European patent no. 0324892 filedby the present applicant.

These machines usually comprise a pay-off unit that feeds a film from areel, associated with a spreader/applicator unit that spreads a smallamount of adhesive (about 1-2 g/m²) onto the surface of the film as itadvances, and a second pay-off unit that feeds from a second reel a filmdestined to be bonded to the preceding film in a bonding unit, whichalso contains a rereeler onto which the film obtained is wound.

Bonded materials consisting of several layers of films are used in anumber of industries. For example, in the packing and food industries,multilayer films are required which may comprise a layer of materialsuitable to come into contact with foodstuffs, a second layer that isimpermeable to liquids or gases, a third layer that provides sufficientstrength, and other layers which may consist, for example, of printablematerial, heat-sealable material and the like.

A series of in-line bonding machines are normally used to manufacturemultilayer films; two films are bonded in a first machine and thenconveyed to the second machine, in which they are bonded to a thirdfilm.

This solution is obviously not only cumbersome, but also extremelyexpensive in terms of both the initial investment and the maintenanceand running costs, especially as each of these machines can be up to10-15 metres long and require several thousand Kw to run.

The present invention, which falls into this sector, relates to amachine, and the relevant method, designed to bond up to three filmssimultaneously, which is very compact and absorbs much less energy thanconventional systems.

In particular, the machine according to the invention operates by usingtwo methods of bonding a 3-ply film, depending on the materials used.

The first method involves simultaneous bonding of three films, two ofwhich are spread with an adhesive material by spreader/applicator unitsin a single bonding unit.

The second method involves bonding two films in a first bonding unit andsubsequently bonding them to the third film in a second bonding unit; inthis way different forces, and consequently pressures, can be applied tothe two bonding units depending on the materials used, in order toobtain the best results for the finished product.

These and other characteristics will appear more clearly from thedetailed description set out below, provided by way of example but notof limitation, by reference to the annexed figures wherein:

FIG. 1 is a side view of the layout of the machine, configured forbonding three films by the first method according to the invention.

FIG. 2 is a side view of the bonding zone.

FIG. 3 is a side view of a spreader/applicator unit.

FIG. 4 is a side view of the layout of the machine, configured forbonding three films by the second method according to the invention.

FIG. 5 is a side view of the layout of the machine, configured forbonding two films.

As shown in FIG. 1, the machine according to the invention comprises abonding zone 1, two pay-off units 2 and 3 associated with 2spreader/applicator units 4 and 5, and a third pay-off unit 6.

Pay-off unit 2 comprises a support 7 for a reel 8 that feeds a filmlayer S1, which passes through spreader/applicator unit 4 and is thenbonded in bonding zone 1.

As shown in FIG. 3, said spreader/applicator unit comprises a pair ofrollers 9 and 10 in contact with one another. A seating 11 formedbetween said units constitutes the tank that contains the adhesive to bespread on the films.

The mutual position of rollers 9 and 10 is adjustable with devices ofknown type, so as to leave a space of adjustable thickness, namely a fewtenths of a millimetre, between the two rollers, so that when at leastone of said rollers is rotated it takes up a thin layer of adhesivematerial, the thickness of which depends on the distance between therollers. Said adhesive material is then transferred to a third orintermediate roller 11, which rotates around its axis at a speed greaterthan that of roller 10.

The thickness of the layer of adhesive transferred to roller 11 is thusreduced. Downstream of intermediate roller 11 there is a third roller orapplicator roller 12 driven by a motor, not shown in the figure, whichcauses it to rotate at a speed greater than that of roller 11, so thatthe layer of adhesive material previously transferred from roller 10 toroller 11 is transferred to roller 12, further reducing its thickness.

A small portion of film S1, inserted between applicator roller 12 and apresser roller 13, comes into contact with said applicator roller 12, sothat a layer of adhesive material a few microns thick is transferredonto said film.

Said spreader unit, which is already known in itself, substantiallycorresponds to the spreader unit described in the above-mentionedEuropean patent 0324892.

Pay-off unit 3 also has a support 14 for a reel 15 which feeds a layerof film S2 destined to be bonded subsequently in bonding zone 1, and isassociated with a spreader/applicator unit 5 identical to unit 4described above.

The third pay-off unit 6 is equipped with a support 36 for a reel 37which feeds a layer of film S3; unlike the other two pay-off rollers, inthis case there is no spreader/applicator unit, because bonding iseffected by the layer of adhesive material deposited on the other twofilms.

Reels of aluminium foil are generally placed on pay-off roller 6; asthis material is thin and not elastic it is rather fragile, andconsequently tears easily. Moreover, especially in the case of routes inwhich it passes over a plurality of transmission rollers, it is liableto form creases which are impossible to eliminate, and remain visible inthe final bonded film.

Bonding zone 1 has two bonding units 16 and 17.

Unit 16 is constituted by a heated bonding calender 18, mounted onabutments 40 of the machine and in contact with a presser roller 19,driven by a motor not shown in the figure, and counter-rotating withsaid calender.

Roller 19 is mounted on a support 20 which, in turn, is hinged to arotating nip 31, whose axis of rotation coincides with that of calender18. A second support 21 for a second roller 22, which is in contact withroller 19 and counter-rotates with it, is also hinged to calender 18.

The rod of a hydraulic actuator 23 is fixed to the end of support 21.The pressure exerted by roller 21 on roller 19 can be regulated via saidactuator, and the pressure exerted on bonding calender 18 can beindirectly regulated via roller 19.

The rotation of nip 20 allows the point of contact between calender 18and presser roller 19 to be varied, determining the breadth of thecontact arc of the various layers of film bonded on calender 18. More orless heating of the film may be required during bonding, depending onthe materials used, said heating being regulated on the basis of thetime for which the film comes into contact with the calender or thebreadth of the contact arc with the calender.

The second bonding unit 17 is similar to the one just described, but isnot fitted with a rotating nip.

Bonding calender 24, mounted on abutments 40 of the machine, is incontact with a counter-rotating presser roller 25 and mounted on asupport 26 hinged to abutments 40.

A second roller 27, in contact with roller 25, is mounted on a secondsupport 28, also hinged to abutments 40, to the end of which the rod ofa hydraulic actuator 29, having the same function as actuator 23described above, is connected.

Two cooling calenders 30, designed to cool the bonded film before it iswound onto drum 32 to form the finished product reel, are installed atthe exit from the bonding units.

As this is a 3-ply film (ie. one consisting of three layers), andconsequently fairly thick, the winding unit is equipped with a verticalpresser 33 fitted with a roller 34 which is kept pressed against reel 35to compact the bonded film as much as possible.

The pressure exerted by the presser roller can be regulated by adjustingthe pressure of the hydraulic fluid in actuator 38 connected to roller34.

The device runs vertically to follow the increase in diameter of reel 35as the bonded film is rereeled.

The operation of the machine according to the invention is describedbelow, according to the different methods of use.

In FIG. 1, the machine according to the invention is configured to bondthree films simultaneously in the same bonding unit.

The present invention also relates to a method for bonding three filmsusing the same bonding unit; this method comprises the followingoperations:

-   -   i) two films are fed and guided into the spreader/applicator        units designed to apply an adhesive material onto said films;    -   ii) the third film is fed;    -   iii) the three films are directed towards the bonding zone where        the films are adhesively bonded to each other; and    -   iv) the final film composed of the layers bonded by means of the        adhesive material is taken out.

No adhesive material is applied to the third film that is fed duringstage (ii). More in particular, in the method of the present inventionfilm S1 is unwound from reel 8 and conveyed to spreader/applicator unit4 where, as it runs over presser roller 13, it comes into contact withapplicator roller 12 which leaves a thin layer of adhesive material onthe upward-facing surface A of the film.

Film S1 is then conveyed to bonding zone 1 via a series of idle rollers.

Similarly, film S2 is unwound from reel 15 and sent tospreader/applicator unit 5, which deposits a layer of adhesive materialon the upward-facing surface B.

Film S3, unwound from reel 37, passes over a pre-heating calender 39,which increases the film temperature to facilitate bonding, beforereaching bonding zone 1.

The three films S1, S2 and S3, guided by a set of idle rollers, convergein zone 1 where said third film S3 is inserted between the first twofilms S1 and S2, with adhesive spread on sides A and B, respectivelyadjacent to the sides C and D of the third film S3; the three films arethen wound onto heated calender 18 and caused to adhere to one anotherby the pressure exerted by roller 19, which presses film F1, now bonded,onto calender 18.

Bonded film F1 then passes over the two cooling calenders 30 and, oncecooled, is wound onto drum 32 to form finished product reel 35. In thiscase the second bonding unit 17 is not used; film F1 runs over calender24 but presser roller 25 is disengaged, and does not exert any pressureon film F1.

The present invention also relates to a method wherein the machine isconfigured to bond three films in two different stages as illustrated inFIG. 2.

Said method comprises the following operations:

-   -   i) two films are fed and guided into the spreader/applier units        designed to apply an adhesive material to said films;    -   ii) a third film is fed;    -   iii) two of said films, one of which is spread with adhesive        material, and the other without adhesive coating, are guided        towards a first bonding zone where the adhesion action of the        two said film occurs;    -   iv) the two previously bonded films and the other film spread        with adhesive material are guided towards a second bonding unit        where the adhesion bonding of the three films occurs;    -   v) the final film composed of the various layers of film bonded        to one another by means of an adhesive material, are taken out.

More particularly the aforesaid method for bonding a total of threefilms during two separate stages involves the operations describedbelow:

-   -   the stage relating to the unwinding of films S1, S2 and S3 and        application of the layer of adhesive material to films S1 and S2        is identical to the one described above.

Film S2, with the layer of adhesive material on its upper surface B, andfilm S3, are conveyed, via idle rollers, to the bonding zone, where theyare wound onto calender 18, caused to adhere together and compacted bypresser roller 19.

Film S1, after passing over guide roller 41, enters the second bondingunit, to which bonded films S2-S3 output from the first bonding unit arealso conveyed; here, film S1, partly wound onto calender 24, and bondedfilms S2-S3, are caused to adhere together by the pressure of roller 25,driven by actuator 29. The final bonded film F2 is then cooled bycalenders 30 and wound onto reel 35.

If only two layers of film need to be bonded (2-ply film), it issufficient to eliminate one of the two reels that pay out the filmspread with the layer of adhesive material, ie. film S1 or S2.

An example of a configuration of the machine is shown in FIG. 5.

In this case film S2, with the layer of adhesive material, and film S3,are fed and then bonded in the first bonding unit by the same procedureas described above.

Alternatively, both reels which feed the film with the layer of adhesivematerial can be kept mounted and used alternately with the other filmwithout adhesive; in this way it would be possible to manufacture twodifferent types of 2-ply film without reconfiguring the machine, thussaving a considerable amount of time.

The machine and the method according to the invention are highlyinnovative and flexible, because it enables different types of film,consisting of up to three films, to be obtained with a compact machinethat is easily adaptable to the different types of work to be performed.

An expert in the field could devise various modifications andvariations, all of which should be deemed to fall within the ambit ofthis invention.

1. Machine for bonding up to three films characterised in that itcomprises: a first unit designed to unwind a first film associated witha spreader/applicator unit to apply an adhesive material to one surfaceof said film; a second unit designed to unwind a second film associatedwith a spreader/applicator unit to apply an adhesive material to onesurface of said film; a third unit designed to unwind a third film; anda fourth unit comprising two bonding machines designed to join thevarious layers of film together.
 2. Machine for bonding up to threefilms according to claim 1, wherein said bonding units comprise abonding calender, onto which the various layers of film are wound, andat least one presser roller which is subject to the action of hydraulicactuators.
 3. Machine for bonding up to three films, which may be madeof different materials, as claimed in claim 2, wherein the two bondingunits are positioned between the two pay-off/applicator units. 4.Machine for bonding up to three films according to claim 1, wherein atleast one bonding unit is mounted on a rotating nip which allows thepoint of contact between the calender and the presser roller to bevaried.
 5. Machine for bonding up to three films according to claim 1,wherein said spreader/applicator units include at least one pick-uproller designed to take up a layer of adhesive from a tank, and at leastone transfer roller designed to transfer the adhesive material from saidpick-up roller to an applicator roller over which the paid-out filmtravels.
 6. Machine for bonding up to three films according to claim 1,wherein presser means, subject to the action of hydraulic actuators,which compact the reel during winding of the bonded film, thusconsiderably reducing its size.
 7. Method for bonding three films usingsolventless adhesive material, wherein: i) two films are fed and guidedinto spreader/applicator units designed to apply an adhesive material tosaid films; ii) a third film is fed; iii) the three films are guided toa bonding zone where the adhesion action between the films occurs; iv)the final film, consisting of layers of film bonded together by anadhesive material, is then taken up.
 8. Method of bonding three films,according to claim 7, comprising a first film S1 which is fed from areel 8 and guided into a first spreading unit 2 designed to spread afine layer of adhesive onto a side A of said first film S1; a secondfilm S2 which is fed from a reel 15 and guided into a first spreadingunit 3 designed to spread a fine layer of adhesive onto a side B of saidfirst film S2; a third film S3 which is fed from a reel 37: wherein thatthe three layers of film are guided towards a bonding zone 1, whereinsaid third film S3 is inserted between the first two films S1 and S2,with sides A and B spread with adhesive; sides A and B beingrespectively adjacent to sides C and D of the third film S3 not coatedwith adhesive, in such a manner, that the three layers of film arebonded together, there being also provided a bonding machine 16comprising a heated bonding calender 18 whereon the three layers of filmS1, S2, and S3 are partially wound, and a presser roller 19 rotating inthe inverse direction to the calender 18, designed to exert a certainlevel of pressure on a limited area of the three layers of film tofacilitate the adhesive bonding; on exit, the bonded film F1 is thenguided towards one or more cooling calenders 30, on which it ispartially wound to be collected on a drum 32 to form the reel 35 of thefinished product.
 9. Method for bonding three films, using a solventlessadhesive, wherein: i) two films are fed and guided intospreader/applicator units designed to apply an adhesive material to saidfilms; ii) a third film is fed; iii) two of said films, one of which isspread with adhesive material, and the other without adhesive coating,are guided towards a first bonding zone where the adhesion action of thetwo said film occurs; iv) the two previously bonded films and the otherfilm spread with adhesive material are guided towards a second bondingunit where the adhesion bonding of the three films occurs; v) The finalfilm composed of the three layers bonded to one another by means of anadhesive material is taken off.
 10. Method for bonding three filmsaccording to claim 9, comprising: a first film S1 which is fed from areel 8 and guided into a first spreading unit 2 designed to spread afine layer of adhesive material on a side A of said first film S1; asecond film S2 which is fed from a reel 15 and guided into a firstspreading unit 3 designed to spread a fine layer of adhesive materialonto a side B of said first film S2; a third film S3 which is fed from areel 37; wherein that films S2 and S3 are guided towards a first bondingzone 1, wherein said B of film S2 is placed in contact with side D offilm S3, a bonding unit 16 being provided, comprising a heated bondingcalender 18 on which two layers of film S2 and S3 are partially wound,and a presser roller 19, rotating in a counter wise direction inrelation to the calender 18 designed to exert a certain pressure on alimited area of the two layers of film to facilitate the adhesion ofsaid first bonded film S2-S3, being guided into a second bonding unit 17comprising a calender 24 on which are wound said bonded films S2-S3 andthe first film S1, paid out from reel 8 and previously spread withadhesive, and a presser roller 25, rotating in a counter wise directionin relation to calender 24, designed to exert a certain pressure on alimited area of the three layers of film S2-S3 and S1 to facilitateadhesion; on exit, the bonded film F2 being then guided towards one ormore cooling calenders 30 on which it is wound partially prior to beingcollected on a drum 32 to form the reel 35 of finished product.